The invention relates to an x-ray analyzing system for x-ray scattering analysis comprising: an x-ray source for generating a beam of x-rays propagating along a transmission axis, at least one hybrid slit with an aperture which defines the shape of the cross-section of the x-ray beam, a sample on which the x-ray beam shaped by the hybrid slit is directed, and an x-ray detector for detecting x-rays originating from the sample, wherein the hybrid slit comprises at least three hybrid slit elements, each hybrid slit element comprising a single crystal substrate bonded to a base with a taper angle α≠0, the single crystal substrates of the hybrid slit elements limiting the aperture.
Such an x-ray analyzing system is known from WO 2011 086 191 A1.
X-ray measurements, in particular x-ray diffraction (XRD) and small angle x-ray scattering (SAXS) measurements are used for chemical analysis and structural analysis of samples in a variety of applications.
In particular in SAXS measurements using laboratory sources it is important to have a high photon flux and a low background. The photon flux is important to have short data acquisition times and the low background is important since the scattering signal is often very low. The aperture of the slit defines the size and shape of the beam cross-section and the divergence of the beam which are important parameters for the achievable resolution.
By directing x-rays to an aperture of a slit of polycrystalline material parasitic diffraction can happen, which results in a decreased signal to noise ratio. In order to limit the divergence of the x-ray beam it is known to use three aperture slits within the optical path of the x-ray beam. However, this results in a reduction of the photon flux and therefore in an increased measurement time.
Li Youli; Beck Roy; Huang Tuo; et al. (Scatterless hybrid metal-single-crystal slit for small angle x-ray scattering and high resolution x-ray diffraction; JOURNAL OF APPLIED CRYSTALLOGRAPHY Volume: 41 Pages: 1134-1139 (2008)) suggested the use of hybrid slits where the edges are made of single crystals such as Germanium or Silicon. The hybrid slits comprise a metal base on which a rectangular single crystal substrate is mounted, wherein the single crystal substrates of the hybrid slit elements limiting the aperture. Parasitic scattering due to total reflection and scattering at grain boundaries can be avoided. The introduction of hybrid slits has made it possible to use only two slits (square pinholes) and still have a low background.
WO 2011 086 191 A1 discloses an x-ray analyzing system for SAXS measurements using hybrid slits comprising two sets of two hybrid slit elements being arranged opposite with respect to each other to form a rectangular or square aperture. In SAXS measurements the resolution is determined by the smallest achievable scattering angle which in turn depends on the size of the cross-section of the direct beam which is blocked by an appropriate beamstop. Since the minimal beamstop size is determined by the distance from the center to the outermost point of the beam cross-section, the resolution of the x-ray analyzing system known from WO 2011 086 191 A1 is limited by the dimensions of the hybrid slit elements.
It is the object of the invention to suggest an x-ray analyzing system with improved resolution and signal to noise ration.